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Stopping the Nematode Threat to Potatoes with Fumigation

Cyst nematodes are a huge potential threat to potato production in the US. Nematodes are microscopic unsegmented worms. Roots of infected plants contain minute, white bodies of females. When a female dies, its cuticle forms a protective cyst containing 200 to 500 eggs. Cysts containing viable eggs can persist in the soil for up to 20 years. When potatoes are planted, root exudates stimulate juvenile nematodes to emerge from eggs. The juveniles locate and enter potato roots. They cut through cell walls and feed. Infection with nematodes reduces root biomass, which can lead to stunting of plants, yellowing and wilting of foliage and small tubers. Heavy infestations often results in total crop loss. Potato cyst nematodes are widespread in many countries, but only two localized infestations have occurred in the US. The latest infestation, found in Idaho in 2006, has led to a strict treatment program with fumigants.

“Two species of potato cyst nematode are found in the United States: Globodera pallida, the pale cyst nematode (PCN), was first found in Idaho in 2006, whereas the golden nematode, G. rostochiensis (GN), was first found in New York in 1941. Both species are regulated under a Federal Domestic Quarantine Order (USDA-APHIS) and parallel State Rules (Idaho State Dept. of Agriculture, New York State Dept. of Agriculture), and eradication effects are underway.

While some resistance to PCN is present in potato varieties grown in Europe and elsewhere in the U.S., there is no resistance in most of Idaho’s signature russet varieties.

The presence of G. pallida in Idaho has been viewed with alarm by other states and countries that import Idaho potatoes and other farm products. After the initial Idaho PCN detection in 2006, markets for Idaho fresh potato products and nursery stock were lost for Canada, Mexico, and Korea. Japan temporarily closed the market for all U.S. potatoes, and continues to disallow Idaho shipments. Consequently, eradication of PCN is a top priority for the Idaho potato industry, including the Idaho Potato Commission, the Idaho State Department of Agriculture, and USDA-APHIS. Millions of dollars have been spent in Idaho in eradication efforts. A critical component of this work has been treatment of infested fields with the fumigant methyl bromide (MeBr), which has been ongoing since the spring of 2007. Lab tests conducted after each treatment indicate a 95% viability reduction after one year’s fumigation, and over 99% viability reduction after successive treatments.”

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